Rack-and-pinion gear mechanism

ABSTRACT

A rack and pinion gear mechanism includes a rack forming member having a rack; a pinion gear which engages releasably with the rack of rack forming member; and an elastic member which contacts with one portion of the rack forming member and deformed by an elastic deformation corresponding to a displacement of the rack forming member by a confliction of tooth points, the one portion is located opposite side to a tooth of the rack that contacts firstly with a tooth of the pinion gear and the gear mechanism further includes a positioning means to fix the elastic member in a cantilever manner to define a positioning of a free end of the elastic member in height.

This application is the national phase under 35 U.S.C. § 371 of PCTInternational Application No. PCT/JP01/09351 which has an Internationalfiling date of Oct. 24, 2001, which designated the United States ofAmerica.

TECHNICAL FIELD

The present invention relates to a rack and pinion gear mechanism bywhich an engagement and its releasing can be performed between a rackand a pinion gear.

BACKGROUND ART

As a rack and pinion gear mechanism in the prior art technology, it iswell known, for example, that is disclosed in Japanese Laid Open PatentSho 63-176857 patent gazette.

FIG. 1 is a front view to show a constitution of the rack and piniongear mechanism in the prior art technology which is disclosed in theabove mentioned Laid Open patent gazette. In the drawing a referencenumeral 1 designates a main body rack, 2 designates a conveying means tocarry pinion series 3A, 3B, 3C and the like. The main body rack 1 isfixed on the main body flame by pins 5 and 6. In a pinion introducingside (which is shown as right side in FIG. 1) of the main body rack 1, aintroducing segment rack 7 is arranged capable of rocking in verticaldirection around a pin 6 as an axis contacting with the main body rack1. At a junction point 8 of an end portion of the main body rack 1 andan end portion 7A of the introducing segment rack 7, a pitch line 11 intooth depth direction of the introducing segment rack 7 and a pitch line13 in tooth depth direction of the main body 1 are matched. And theintroducing segment rack 7 is arranged in relation to the main body rack1 such that a gear pitch 9 of the introducing segment rack 7 at thejunction point 8 is made aligned with a gear pitch 10 of the main bodyrack 1. An end portion 7B of the pinion introducing side of introducingsegment rack 7 is held so that the pitch line 11 in tooth depthdirection becomes at least lower than the pitch line 13 of tooth depthdirection of the main body rack 1 in a predetermined amount 12. At thispoint the above mentioned amount 12 is maintained by means that a block15 which is built as one body in the introducing segment rack 7 ispushed against a stop pin 14 by a boost up force of spring 16.

And a distance 20 between the stop pin 14 and an end surface of the endportion 7B of pinion introducing side of the introducing segment rack 7is set less than one half of the gear pitch. The spring 17 is an elasticmember to press the introducing segment rack 7 to the main body rack 1.A force generated in a tooth surfaces when the introducing segment rack7 and the pinion 3B and the like are engaged, can be absorbed by adisplacement and its return in longitudinal direction of the introducingsegment rack 7.

Hereinafter operation of the mechanism will be explained.

When the pinion 3B, for example, usually comes from right hand directionof the drawing and arrives on the introducing segment rack 7, a toothpoint of the pinion 3B and a tooth point of the introducing segment rack7 interfere together. At this point the introducing segment rack 7 rocksdownward around axis of the pin 6 as a center to absorb the forcegenerated at the tooth points. By this movement disadvantages such as amalfunction of the gear mechanism, a damage of driving motor, a breakageof teeth and the like are prevented.

However in the rack and pinion gear mechanism in the prior arttechnology there has been a problem that a constitution of the gearmechanism is too complicated because a means to prevent thedisadvantages which is generated by a confliction of the tooth points,is composed of the introducing segment rack 7 that moves to a directionto release an engagement when the confliction of tooth points occurs,the spring 16 that always presses the introducing segment rack 7 upwardto hold it at a predetermined position and the spring 17 that urges thegears in a direction for the engagement and makes the gears smoothlyengaged when the engagement is released.

The present invention has been made to solve the above described problemand it is an object of the invention to provide a rack and pinion gearmechanism by which the disadvantages caused by confliction of the toothpoints can be prevented with a simple constitution.

DISCLOSURE OF THE INVENTION

The rack and pinion gear mechanism in accordance with the presentinvention includes a rack forming member having a rack; a pinion gearwhich engages releasably with the rack of rack forming member; and anelastic member which contacts with one portion of said rack formingmember, which is located opposite side to a tooth of the rack thatcontacts firstly with a tooth of said pinion gear and is deformed by anelastic deformation corresponding to a displacement of the rack formingmember by a confliction of tooth points. By this arrangement an effectis produced that an occurrence of disadvantages such as a damage ofdriving motor, a breakage of teeth and the like caused by theconfliction of tooth points can be avoided, though it has merely asimple constitution in comparison with the gear mechanism in the priorart technology, the elastic member can be deformed by the elasticdeformation corresponding to a displacement of the rack forming memberhaving the rack when the confliction of tooth points occurs at verybeginning of the engagement.

The rack and pinion gear mechanism in accordance with the presentinvention is arranged such that the elastic member contacts with the oneportion of rack forming member at just before and just after beginningof the engagement between the rack and the pinion gear, and the elasticmember is apart from the rack forming member when the engagement iscontinued. By this arrangement an effect is produced that the rackforming member can be surely reset utilizing an elasticity of theelastic member when it need, and at the same time the contact betweenthe elastic member and the rack forming member can be avoided tosuppress the sliding load as low as possible when it does not need.

The rack and pinion gear mechanism in accordance with the presentinvention further includes a positioning means to fix the elastic memberin a cantilever manner to define a positioning of free end of theelastic member in height. By this arrangement an effect is produced thata decrease of durability in operation can be avoidable because a heightof the elastic member can be adjusted in order that the elastic memberis slightly contacted with one portion of the rack forming member justbefore and just after beginning of the engagement, and the sliding loadof elastic member against the rack forming member can be suppressed aslow as possible.

The rack and pinion gear mechanism in accordance with the presentinvention is arranged such that a tooth of the rack which firstlycontacts with a tooth of the pinion gear at the engagement with thepinion gear, is made lower than the other teeth in its height of toothtop. By this arrangement an effect is produced that occurrence of theconfliction of tooth points can be decreased and the smooth engagementcan be attained.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view to show a constitution of rack and pinion gearmechanism in the prior art technology.

FIG. 2 is a perspective view to show a rack and pinion gear mechanism inaccordance with embodiment 1 of the present invention in a state justbefore an engagement of tooth points occurs.

FIG. 3 is a front view of the rack and pinion gear mechanism shown inFIG. 2.

FIG. 4 is an enlarged perspective view to show a relevant part of therack and pinion gear mechanism shown in FIG. 2.

FIG. 5 is a perspective view to show the rack and pinion gear mechanismshown in FIG. 2 to FIG. 4 in a state just after an engagement has beenbegun without an occurrence of the confliction of tooth points.

FIG. 6 is a perspective view to show a state that the engagement isproceeded from the state the engagement has been begun as shown in FIG.5.

FIG. 7 is a front view to show an action of the rack when it is in theengagement shown in FIG. 5 and FIG. 6.

FIG. 8 is a perspective view to show the rack and pinion gear mechanismshown in FIG. 2 to FIG. 4 in a state just after an engagement has beenbegun with an occurrence of the confliction of tooth points.

FIG. 9 is a front view to show an action of the rack when it is in astate of the engagement with the confliction of tooth points.

BEST MODE FOR CARRYING OUT THE INVENTION

For explaining the present invention in more detail, best mode forcarrying out the invention will be described hereinafter with referenceto the accompanied drawings.

EMBODIMENT 1

A rack and pinion gear mechanism in accordance with embodiment 1 of thepresent invention can be applied to, for example, a driving a diskcarrying mechanism (not shown in the drawings) which holds a compactdisk (hereinafter it is refereed to as “CD”) to carry it to apredetermined position and at the same time evacuates from a projectionsurface of CD when it is in a reproducing state in a CD driving device(not shown in the drawings) by which the reproducing of opticalrecording media such as CD is performed, however, this embodiment 1 isonly an example and the present invention is not limited only to thisembodiment 1.

FIG. 2 is a perspective view to show a rack and pinion gear mechanism inaccordance with embodiment 1 of the present invention in a state justbefore an engagement of tooth points occurs, and FIG. 3 is a front viewof the rack and pinion gear mechanism shown in FIG. 2. FIG. 4 is anenlarged perspective view to show a relevant part of the rack and piniongear mechanism shown in FIG. 2, and FIG. 5 is a perspective view to showthe rack and pinion gear mechanism shown in FIG. 2 to FIG. 4 in a statejust after an engagement has been begun without an occurrence of theconfliction of tooth points. FIG. 6 is a perspective view to show astate that the engagement is proceeded from the state the engagement hasbeen begun as shown in FIG. 5, and FIG. 7 is a front view to show anaction of the rack when it is in the engagement shown in FIG. 5 and FIG.6. FIG. 8 is a perspective view to show the rack and pinion gearmechanism shown in FIG. 2 to FIG. 4 in a state just after an engagementhas been begun with an occurrence of the confliction of tooth points,and FIG. 9 is a front view to show an action of the rack when it is in astate of the engagement with the confliction of tooth points. At thispoint in the drawings an end portion of rack which is nearer to a piniongear is called as a “front end” and an end portion of the rack which isfarther to the pinion gear is called as a “back end” as far as it is notespecially refereed.

In the drawings a reference numeral 21 designates a rack plate which hasa long plate shape. In an inside front of the rack plate 21 a continuoslength of opening portion 22 is made in a position which is near to thepinion gear that will be described later. A width of this openingportion 22 is made wider than an outer diameter of the pinion gear(diameter of addendum circle) that will be described later. In a underedge portion of the opening portion 22 a rack 23 is made which iscomposed of an arrangement of teeth that is disposed along a straightline. In this embodiment 1, the rack is made such that height of a firsttooth 23 a of the rack 23 (tooth height) is lower than the other teethin order to absorb a confliction of tooth points between the rack 23 anda pinion gear that will be described later.

In the rack plate constituted as described above, a back side guidingpin 24 and a front side guiding pin 25 which are separated each otheralong its long direction, are disposed at a surface opposing to amounting table that will be described later. The back side guiding pin24 is disposed at a back position which is apart from the openingportion 22, and the front side guiding pin 25 is disposed at a frontposition which is near to the opening portion 22. These back sideguiding pin 24 and front side guiding pin 25 are respectively composedof a head portion 24 a and 25 a which have a large outer diameter and afoot portion 24 b and 25 b (not shown) which have a smaller outerdiameter than the head portions.

Also in a lower front portion of the rack plate 21, a sliding portion 26is formed, which slides and contacts with an elastic member that will bedescribed later. This sliding portion 26 is composed of a slidingsurface 26 a which receives a sliding by the elastic member that will bedescribed later, a front curved surface 26 b which is formed in front ofthe sliding surface 26 a to absorb a mechanical shock by a contact withthe elastic member that will be described later when the rack plate 21moves forward, and a back curved surface 26 c which is formed at theback of the above mentioned sliding surface 26 a to absorb themechanical shock by the contact with the elastic member that will bedescribed later when the rack plate 21 moves backward.

A reference numeral 27 designates the mounting table having a long plateshape, and the mounting table is formed on a chassis (not shown) of theabove mentioned CD driving device (not shown).

The mounting table 27 has two guiding grooves which are a back sideguiding groove 28 and a front side guiding groove 29 and they areextending along their long direction and separated each other along thesame direction. The back side guiding groove 28 is mainly composed of acircular groove portion 28 a through which head portion 24 a of the backside guiding pin 24 can be inserted, and a straight groove portion 28 bwhich is formed continuously to the circular groove portion 28 a havinga width that is defined within a range between outer diameters of thehead portion 24 a and the foot portion 24 b of the back side guiding pin24.

Also the front side guiding groove 29 is mainly composed of a circulargroove portion 29 a through which head portion 25 a of the front sideguiding pin 25 can be inserted, and a straight groove portion 29 b whichis formed continuously to the circular groove portion 29 a having awidth that is defined within a range between outer diameters of the headportion 25 a and the foot portion 25 b of the front side guiding pin 25.In this respect in the straight groove portion 29 b there is provided aconcave portion 30 at a position where the circular groove portion 29 ais adjoining. The concave portion 30 is composed of a falling portion 30a which falls from the straight groove portion 29 b, a flat portion 30 bwhich is formed continuously to a lowest portion of the flat portion 30a and is parallel to the straight groove portion 29 b, and a risingportion 30 c which is formed continuously to the flat portion 30 b andrises to the straight groove portion 29 b. At this point a distancebetween an upper edge portion of the straight groove portion 29 b andthe flat portion 30 b of the concave portion 30 is defined smaller thanthe outer diameter of head portion 25 a of the front side guiding pin25.

At a lower edge portion of the mounting table 27, a concave portion 31is provided in a vicinity of the above mentioned concave portion 30 toperform a height adjusting of the elastic member that will be describedlater.

On the mounting table 27 constituted as described above, a pinion gear32 is rotatably fixed to be made enable to engage with the rack 23 ofrack plate 21. At the same time on the mounting table 27 a driving motor34 to transfer a driving force through a series of idler gears 33 to thepinion gear 32.

Also on the mounting table 27 a leaf spring (elastic member) 35 isattached in a cantilever manner. This leaf spring 35 is composed of abase portion 35 b which has a screw hole 35 a for a fixing screw (notshown) to fasten the leaf spring 35 onto the mounting table 27, aprotruding portion 35 c having an inverted V shape which is formed in afree end side that is extending forward from the base portion 35 b, anda engaging portion 35 d which is formed continuously to the protrudingportion 35 c to engage with the concave portion 31 of mounting table 27.The leaf spring 35 is supported at the base portion 35 b by the mountingtable 27 and it is set such that the protruding portion 35 c urges therack plate 21 always upward. However, by means that the engaging portion35 d of the leaf spring 35 is engaged with the concave portion 31 ofmounting table 27, a urging of 21 by the protruding portion 35 c of leafspring 35 is regulated in a level that the rack plate 21 slightlycontacts with the protruding portion 35 c and the rack plate 21 isslidable without any large load, thereby a height of the protrudingportion 35 c is regulated. At the same time because the back sideguiding pin 24 and the front side guiding pin 25 are not pushed torespective upper edge portions of the back side guiding groove 28 andthe front side guiding groove 29, respective large sliding loads to theback side guiding pin 24 and front side guiding pin 25 can be avoided.

A reference numeral 36 designates a trigger. When at a timing that, forexample, a CD is carried to a reproducing position or to a exchangingposition, a command is initiated from a CPU (not shown), the trigger 36pushes a back end portion of the rack plate 21 forward to engage therack 23 and the pinion gear 32, thereby it encourages a beginning ofaction for a rack and pinion gear mechanism which is constituted asabove described.

Hereinafter an operation of the mechanism will be explained.

At first before an operation is initiated, the back side guiding pin 24and the front side guiding pin 25 of rack plate 21 are supported in astate that they are inserted into the circular groove portions 28 a and29 a of back side guiding groove 28 and front side guiding groove 29.

Next as shown in FIG. 2 to FIG. 4, when at a timing, for example, CD iscarried to a reproducing position or to a exchanging position, a commandis initiated from the CPU (not shown), the trigger 36 pushes back endportion of the rack plate 21 forward. After the trigger 36 pushes therack plate 21, the driving motor 34 begins a driving by a command fromthe CPU (not shown) as well, the driving force is transferred throughthe series of idler gears 33 to begin a rotation of the pinion gear 32.When the rack plate 21 begins to go forward along an arrow X1 directionby the above mentioned pushing of trigger 36, a first tooth 23 a of therack 23 and the pinion gear 32 begins to contact. In this respect bythis embodiment 1 of the present invention because the tooth height ofthe first tooth 23 a of rack 23 is made lower than other teeth of therack 23, the confliction of tooth points can be reduced as much aspossible thereby a smooth engagement can be realized.

By this arrangement, the confliction of tooth points is not generatedusually in this embodiment between the rack 23 and the pinion gear 32.In this case respective teeth tops are deeply inserted to respectiveroot of teeth, a smooth engagement is achieved. By this engagement therack plate 21 is carried forward along the direction of arrow X1, andthe back side guiding pin 24 and the front side guiding pin 25 areguided along the back side guiding groove 28 and the front side 29. Atjust before and just after beginning of the engagement, because theprotruding portion 35 c of leaf spring 35 supports the rack plate 21with sliding and contacting onto the sliding portion 26, the front sideguiding pin 25 can pass over the concave portion 30 of front sideguiding groove 29 and arrives at the straight groove portion 29 b.Because the back side guiding pin 24 arrives directly at the straightgroove portion 28 b from the circular groove portion 28 a, a height ofwhole rack plate 21 is not changed at before and after of the engagementand constant always.

In this respect a reference symbol A1 in FIG. 7 designates a posture anda position of the rack plate 21 just before the engagement correspondingto FIG. 2 to FIG. 4, A2 designates a posture and a position of the rackplate 21 at the engagement corresponding to FIG. 5, and A3 designates aposture and a position of the rack plate 21 just after the engagementcorresponding to FIG. 6.

If by any possibility the confliction of tooth points occurred, it canbe absorbed by means that the leaf spring is deformed by an elasticdeformation caused by a force generated by the confliction of toothpoints to rotate the rack plate 21 along a direction shown by an arrowY1 around the back side guiding pin 24 as a center. By this arrangementmalfunction and the like by the confliction of tooth points is avoided.Just after the absorption of occurrence of confliction, the rack plate21 in a state of rotation is reset to an original position along adirection shown by an arrow Y2 by an elastic reset of the leaf spring35. By this arrangement the respective teeth tops are deeply inserted torespective root of teeth, thereby the smooth engagement is achieved.

In a state after the rack plate 21 is reset, the protruding portion 35 cof leaf spring 35 moves away from sliding portion 26 of the rack plate21, and the back side guiding pin 24 and the front side guiding pin 25are guided only by the straight groove portion 28 b of back side guidinggroove 28 and the straight groove portion 29 b of front side guidinggroove 29.

In this respect a reference symbol B1 in FIG. 9 designates a posture anda position of the rack plate 21 just before the confliction of toothpoints occurs, B2 designates a posture and a position of the rack plate21 at the confliction of tooth points corresponding to FIG. 8, and B3designates a posture and a position of the rack plate 21 just after theconfliction of tooth points occurs. A reference symbol C1 in FIG. 9designates a posture and a position of the leaf spring 35 when the rackplate 21 is in a posture and position of B1 and B3, C2 designates aposture and a position of the leaf spring 35 when the rack plate 21 isin a posture and position of B2.

As above described, in any cases when the confliction of tooth pointsoccurs or does not occur, the driving force by the driving motor 34 istransferred to the pinion gear 32 in order to reversely rotate thepinion gear 32 when the rack plate is returned backward along thedirection that arrow X2 shows. By this action the rack plate 21 isreturned backward, thereby the engagement between the rack 23 and thepinion gear 32 is released at the first tooth 23 a of rack 23 sidefinally, then a backward movement of the rack plate 21 is stopped. Asabove described when the rack plate 21 is moved backward, a posture anda height of the rack plate 21 are kept from a beginning of backwardmovement till the pinion gear 32 arrives at the first tooth 23 a of rack23 because the back side guiding pin 24 and the front side guiding pin25 are guided only by the straight groove portion 28 b of the back sideguiding groove 28 and by the straight groove portion 29 b of the frontside guiding groove 29. And at a time point from just before to justafter the pinion gear 32 arrives at the first tooth 23 a of the rack 23,the posture and the height of rack plate 21 are kept because the slidingportion 26 of rack plate 21 is contacted with the protruding portion 35c of leaf spring 35 ant it is supported, only when the front sideguiding pin 25 passes over the concave portion 30 of front guidinggroove 29. Accordingly the posture and the height of rack plate 21 arealways kept when the rack plate 21 moves backward.

As above described, in accordance with embodiment 1 of the presentinvention because the gear mechanism is constituted such that the leafspring 35 is provided as the elastic member, though it has merely asimple constitution in comparison with the gear mechanism in the priorart technology, the leaf spring 35 can be deformed by the elasticdeformation corresponding to a displacement (rotating movement) of therack plate 21 having the rack 23 when the confliction of tooth pointsoccurs at very beginning of the engagement between the rack 23 and thepinion gear 32, an effect is produced that an occurrence ofdisadvantages such as a damage of driving motor, a breakage of teeth andthe like caused by the confliction of tooth points can be avoided.

In accordance with embodiment 1 of the present invention an effect isproduced that the rack plate 21 which is shifted with an elasticdeformation of the leaf spring 35 in order to absorb the confliction oftooth points, can be surely reset at the original position utilizing anelasticity of the leaf spring 35 because the leaf spring 35 is arrangedto be apart from the rack plate 21 just before and after a beginning ofthe engagement between the rack 23 and the pinion gear 32, and at thesame time the contact between the leaf spring 35 and the rack plate 21can be avoided to suppress the sliding load as low as possible when therack 23 and the pinion gear 32 are engaged each other.

In accordance with embodiment 1 of the present invention a height of theprotruding portion 35 c can be adjusted in order that the protrudingportion 35 c is slightly contacted with the sliding portion 26 of rackplate 21 just before and just after beginning of the engagement becauseit is constituted that the concave portion 31 is formed on the mountingtable 27 as a positioning means by which the leaf spring 35 is fixed ina cantilever manner and defines a positioning of the protruding portion35 c of free end side of the leaf spring 35 in height. By thisarrangement an effect is produced that a decrease of durability inoperation can be avoidable because the sliding load of protrudingportion 35 c against the rack plate 21 can be suppressed as low aspossible.

In accordance with embodiment 1 of the present invention an effect isproduced that occurrence of the confliction of tooth points can bedecreased and the smooth engagement can be attained because a height ofthe first tooth 23 a of rack 23 is made lower than the other teeth ofthe rack 23, which contacts firstly with a tooth of the pinion gear 32when the engagement with the pinion gear 32 is achieved.

INDUSTRIAL APPLICABILITY

As set forth above, the present invention provides the rack and piniongear mechanism by which the engagement and its release are achievedbetween the rack and the pinion gear, and the present invention isapplicable, for example, in a CD driving device for driving of diskconveying mechanism which holds CD to carry to a predetermined position,and at the same time evacuates from a projection surface of CD when itis in a reproducing state.

1. A rack and pinion gear mechanism comprising: a rack forming memberhaving a rack with a plurality of teeth formed on a first edge of saidrack forming member; a pinion gear which engages releasably with saidrack of said rack forming member; and an elastic member which contactswith one portion of said rack forming member, which is located on anopposite side to a tooth of the rack that contacts firstly with a toothof said pinion gear and is deformed by an elastic deformationcorresponding to a displacement of the rack forming member by aconfliction of tooth points, wherein the rack forming member includes asliding member that has a front curved surface located adjacent tooth ofthe rack that first contacts with the tooth of said pinion, and a flatsurface extending from the front curved surface to a back curvedsurface, the rack forming member only engaging the elastic member at thesliding member.
 2. The rack and pinion gear mechanism according to claim1 wherein said elastic member contacts with the sliding member said rackforming member at just before and just after the beginning of theengagement between the rack and the pinion gear, and the elastic memberis apart from the rack forming member when the engagement is continued.3. The rack and pinion gear mechanism according to claim 2 furthercomprising a positioning means to fix the elastic member in a cantilevermanner to define a positioning of a free end of the elastic member inheight.
 4. The rack and pinion gear mechanism according to claim 1wherein said tooth of the rack which firstly contacts with said tooth ofsaid pinion gear at the engagement with the pinion gear is shorter inheight than the other teeth.